Furnace appliance



Nov. 23, 1943. A. LAIST ETAL FURNACE APPLIANCE Filed Jan. 27, 1942 INVENTOR5 5 .N Y T 5 EN m /m LA Wm.B WA N D mv a H L LL AR I a Patented Nov. 23, 1943 2,334,878 FURNACEAPPLIANCE Alexander Laist and Earl Milton Baldwin, Helena, Mont., assignors to- Anaconda Copper Mining Company, a corporation of Montana Application January 27, 1942, Serial No. 428,365

11 Claims.

This invention relates to furnace appliances, and more particularly to appliances for preventing the clogging of the tuyeres of a metallurgical furnace in which air and fuel are blown through the tuyres into a molten charge when the blowing engine or air compressor stops because of an interruption or failure of power. Such furnaces are. used, for example, for recovering volatile metals such as zinc from lead smelter slags. Air and fuel, usually powdered coal, are blown through the tuyeres into the molten slag in the furnace. The zinc. is reduced to the metallic form and volatilized, and the zinc vapor passing out of the furnace is immediately burned to zinc oxide and is collected in a bag-house or the like.

"Power failures, particularly of electric power,

occur frequently in smelting districts, and cause serious and costly trouble in the furnace operation. The molten-slag stands about four feet above the tuyres in. the furnace, and when the air pressure goes off because of a power failure, the molten slag runs back into the tuyeres and connecting pipes, burning any rubber hose connections, injuring valves and causing a shutdown of the furnace for several hours. Various expedients have heretofore been resorted to in attempts to minimize the operating troubles due to power interruptions, such as the provision of check valves or the like in the tuyere connections, and while such expedients have given some improvement they have not eliminated the troubles, particularly with large furnaces.

The object of the present invention is to provide a novel and improved appliance for preventing the back flow of slag into the tuyeres whenever the blowing engine or the like stops because of power interruptions. In its broad aspect, the invention involves the provision of a source of compressed air normally connected to the compartment supplying the air and fuel to the tuyres, and means responsive to power interruptions for disconnecting the compressed air source from the air-fuel compartment and for directly connecting the tuyeres to the compressed air source whenever the power is interrupted. The normal operating connection between the tuyres and the air-fuel compartment is manually or automatically restored when power returns. In its more complete aspect, the appliance of the invention includes valves in the connections between the compressed air source, the air-fuel compartment and the tuyeres which by a combination of electrical and pneumatic agencies are automatically actuated to effect the contemplated emergency connections between the compressed air. source, the air-fuel compartment and the tuyeres. These and other novel features of the invention will be best understood from the following description taken in conjunction with the accompanying drawing, in which Fig. 1 is a diagrammatic view of the appliance of the invention in the normal operation of the-furnace, and

Fig. 2 is a diagrammatic view of the appliance following a power interruption.

The drawing illustrates, in Fig. 1, the lower corner of a furnace 5 in which the molten slag level is indicated at t. tuyres I extend into the furnace, on opposite sides, well below the slag level 8. Powdered coal and high pressure air, say about pounds persquare inch, are blown into each tuyere through a branch pipe 8 connected to a distributing pipe which in turn is connected to the air-fuel feed pipe iii. For the sake of simplicity, only one twere is shown in the drawing, and only one of the feed pipes It is shown connected to its cooperating distributing pipe 9. In the actual furnace structure one feed pipe Ill supplies air and fuel to half of the tuyeres on one side of the furnace, and hence four such feed pipes are provided. Additional combustion air at a lower pressure is supplied to each tuyre through a branch pipe ll connected to a bustle pipe E2. The branch pipes a and H discharge into chambers l3 and M in the tuycre fitting l5. A check valve l6 between the chambers l3 and M prevents the high pressure air from escaping through the low pressure air pipes when the low pressure air is cut oil by a power interruption, as explained in United States Letters Patent 1,769,146, patented July 1, 1930.

The appliance of the invention provides an adequate supply or reservoir of high pressure air to force against the slag immediately upon the occurrence of any power interruption. To this end, we provide one or more sources of high pressure air in the form of one or more receivers l1. High pressure compressed air is introduced into the receiver (or receivers) ll through a pipe conducts the high pressure air to the air-fuel A plurality of spaced.

compartments 20. These compartments or bins are hermetically tight, and are charged with powdered coal in any appropriate manner. The mixture of high pressure air and powdered coal is blown through the feed pipe Ill and the distributing pipe 9 to the branch pipes 6 of the individual tuyeres.

A three-way tuyere valve or cock 2| is included in each of the feed pipes III. A pipe 22 connects each of the tuyre valves 2| to the high pressure pipe line 8. The tuyere valves 2| are adapted to occupy either of two positions, the first of which is the normal operating position connecting the compartment to the tuyeres fed by the cooperating feed pipe ill, and the second of which is the emergency position connecting the tuyeres directly to the high pressure air source I'I.

The main source of electric power 23 is connected in the conventional manner through an oil switch 24 to the electric motor |2b for operating the blowing engine |2a which supplies low pressure air to the bustle pipe |2. This switch 24 advantageously is equipped with undervoltage and overload trips so that it is opened upon the occurrence of any abnormal power condition such as a power failure. It may be an oil circuit breaker of common construction. A relay switch 251s mechanically connected to and actuated by the switch 24 so that it is normally open but closes (when the switch 24 opens) upon any failure or interruption of the power circuit. The switch 25 is included in an auxiliary electric circuit with a storage battery 26, or other suitable source of electric energy, a manually operated switch 21, and the relay winding 28 of a magnetic switch 29. The magnetic switch 29 is included in a second auxiliary electric circuit, which includes the switch 21, the battery 25 and a motor or equivalent electro-magnetic motive means The motor 30 is operatively connected, by a thrustor mechanism 30a and linkage 30b to a lever or equivalent mechanism 3| for actuating an air control valve 32 included in a pipe 33 connected to the high pressure pipe line It. The motor 30 and associated thrustor mechanism may be built together as a unit. The valve 32 controls the supply of compressed air from the pipe 33 to the pneumatic cylinder or motor 34 having a movable piston or equivalent member 35 operatively connected to a pusher rod 36 for operating the main air-valve l9 and the tuyere valves 2|. When the air control valve 32 is closed as in Fig. 1, the piston 35 is biased to its lower position (as diagrammatically illustrated in Fig. 1) with the rod 36 in its normal operating position, by means of a compression spring 31. The main air valve i9 and the tuyere valves 2| then are in their respective normal operating positions connecting the pipe line l8 to the compartments 20 and the compartments 20 to their respective cooperating feed pipes I0. When the control valve 32 is open as in Fig. 3, high pressure air is admitted to the cylinder 34 and the resulting movement of the piston 35 actuates the rod 36 (upwardly as shown in the drawing). Arms 38 on the rod 36 thereupon move the valve actuating lever 39 of the main valve I9 and similar levers 40 of the tuyre valves 2| to close the main air valve (disconnecting the pipe line |8 from the compartments 20) and to move the tuyere valves to their emergency positions in which the tuyeres are directly connected to the reservoir H.

The main valve I9 is provided with a catch 4| which engages with a latch 42 when this valve is thrown to-its emergency position. The tuyere valves 2| are provided with corersponding catches 43 and latches 44. These catches and latches hold the main and tuyere valves in their emergency position when once they are so thrown, and insure against accidental return of any of the valve to their normal operating positions;

The operation of the appliance is as follows:

With the tuyres blowing compressed air and fuel (from the feed pipes l3) and combustion air (from the bustle pipe l2) into the body of molten slag, or the like, in the furnace, the appliance is in its normal operating position diagrammatically illustrated in Fig. 1. Upon an interruption or failure of the power circuit 23, the switch 25 immediately closes the auxiliary electric circuit including the battery 26 and relay winding 23, thereby closing the magnetic switch 29 and connecting the motor 30 to the battery 26. The motor 30, through the lever 3|, moves the air control valve 32 to connect the cylinder 34 to the receiver l1, and the resultant movement of the piston 35 and rod 33 closes the main air valve l3 and moves the tuyre valves 2| to their emergency positions directly connecting the tuyeres to the reservoir The emergency position of the appliance is illustrated in Fig. 2. The high pressure air directly supplied to the tuyeres prevents molten slag running back into the tuyres, and a suihcient reserve of the high pressure air is available from tank to meet any normal power interruption. During the period of the emergency the check valve l6 operates to disconnect the bustle pipe |2 from the furnace. The motor 3|! may also, if necessary, shut off the coal feeding apparatus by actuating a switch for stopping the motor that runs it. When the supply of power is resumed, the switches 25 and 29 open, as in Fig. 1 thereby de-energizing the motor 30 and permitting the control valve 32 to return to its normal or open position. The return of the valve 32 to its normal position releases the air pressure on the piston 35, enabling the spring 31 to return the piston 35 and pusher rod 36 to their normal operating positions, following which the main air valve l9 and tuyere valves may be reset manually in their normal operating positions (Fig. 1).

In the case of a large furnace, the emergency connection of the tuyres directly to the compressed air reservoir must be effected immediately and automatically upon the interruption of power,

since a delay of even a few seconds may cause such damage as to require a furnace shut-down of several hours. The restoration of the appliance to its normal operating position, when power is resumed, requires no special haste, and hence may be effected by manual operation of latches 42 to 44 inclusive. The switch 21 is used to open the auxiliary circuits when the furnace is shut down for repairs.

We claim:

l. The combination with a furnace having tuyres, an air-fuel compartment normally connected to. said tuyeres for blowing air and fuel therethrollgh into a molten charge in the furnace, a source of compressed air normally connected to said compartment, and a source of power for providing the compressed air, of means responsive to interruptions of said power source for disconnecting said reservoir from said compartment and directly connecting said tuyres to th reservoir whenever the supply of power is interrupted.

2. The combination with a furnace having tuyeres, an air-fuel compartment, a source of compressed air, and a source of power for providing the compressed air, of means including a main valve for connecting said source of compressed air to said compartment, means including a tuyere valve for selectively connecting the tuyres to either said compartment or directly to said source of compressed air, and means responsive to interruptions of said power source for closing said main valve to disconnect the source of compressed air from said compartment and for actuating said tuyere valve to connect said tuyeres directly to said reservoir whenever the supply of power is interrupted.

3. The combination with a furnace having tuyeres, an air-fuel compartment, a source of compressed air, and a source of power for providing the compressed air, of means including a main valve for connecting said source of compressed air to said compartment, means including a tuyre valve for connecting the tuyres to either said compartment for normal operation or directly to said compressed air source for. emergency operation, and means responsive to an interruption of power from said source for closing said main valve to disconnect said compartment from said compressed air source and for actuating said tuyere valve to connect said tuyres directly to said compressed air source.

4. The combination with a furnace having tuyeres, an air-fuel compartment, 2. source of compressed air, and a source of power for providing the compressed air, of means including a main valve for connecting said source of compressed air to said compartment, means includ-' ing a tuyere .valve for connecting the tuyeres either to said compartment for normal orxeration or directly to said compressed air source for emergency operation, valve operating means for simultaneously closing said main valve to disconnect the source of compressed air from said compartment and for positioning said tuyre valve for emergency operation, and electrically operated means connected with said source of power nect said tuyeres directly to said reservoir whenever the supply of power from said power source is interrupted.

7. The combination with a furnace having tuyres, an air-fuel compartment, a source of compressed air normally connected to said compartment, and a source of electric power for providing the compressed air, of a, main valve for connecting and disconnecting said source of compressed air to said compartment, a tuyere valve between said tuyeres and said compartment for selectively connecting the tuyeres either to said compartment or directly to said compressed air source, electrically operated means operativefor actuating said valve operating means upon incompartment from said compressed air source and for actuating said tuyre valve to connect said tuyeres directly to said, reservoir whenever power from the power source is interrupted.

6. The. combination with a furnace having tuyeres, can air-fuel compartment, a source of compressed air, and a source of electric power for providing the compressed air, of means including a main valve for connecting said source of compressed air to said compartment, means including a tuyere valve for selectively connecting the tuyeres either to said compartment or to said compressed air source, and means operatively associated with said source of power and said valves and operated by an independent source of electric energy for immediately and automatically closing said main valve to disconnect said compartment from said compressed air' source and for actuating said tuyere valve to con- 1y associated with said source of power and said valves for simultaneously actuating said main valve to disconnect said compartment from said compressed air source and operating said tuyere valve to connect said tuyeres directly to said compressed air source whenever the supply of power from said power source is interrupted, and restoring the normal connection between said compressed air source and said compartment and the normal connection of said tuyeres to said compartment when the supply of power from said source is resumed.

8. The combination with a furnace having tuyeres, an air-fuel compartment, a source of compressed air, and a source of electric power for providing the compressed air, of means including a main valve for connecting said compressed air source to said compartment, means including a tuyere valve for selectively connecting the tuyeres either to said compartment or to said compressed air source, said valves being arranged to be moved to either of two operating positions in the first of which the main valve is open to connect said compartment to said compressed air source and the tuyere valve connects the tuyres to said compartment and in the second of which the main valve is closed and the tuyere valve connects the tuyeres to said compressed air source, and electrically operated means responsive to interruptions of power from said power source for causing said valves to move to their aforesaid second positions whenever the supply of power is interrupted and to be returned to their aforesaid first positions when the supply of power is resumed.

9. The combination with a furnace having tuyres, an air-fuel compartment, a source of compressed air, and a source of electric power for providing the compressed air, of means including a main valve for connecting said compressed air source to said compartment, means including a tuyere valve for selectively connecting the tuyres either to said compartment or to said compressed air source, said valves being arranged to be moved to either oftwo operating positions in the first of which the main valve is open to connect said compartment to said compressed air source and the tuyere valve connects the tuyeres to said compartment and in the second of which the main valve is closed and the tuyre valve connects the tuyeres directly to said compressed air source, valve moving means for moving said valves from said first position to said second position, an auxiliary electric circuit including a source of electric energy and an electromagnetic switch for openingand closing the circuit, means operatively associated with said source of power for causing said switch to close said auxiliary circuit whenever the supply of power is interrupted and to open said circuit when the supply of power is resumed, and electromotive means included in said circuit and operatively connecte'd to said valve moving means and adapted when energized by the closing of said circuit to actuate said valve moving means to move said valves to their aforesaid second positions.

10. The combination with a furnace having tucompartment and in the second of which the main valve is closed and the tuyre valve coannects the tuyres directly to said compressed air source, valve moving means for moving said valves from said first position to said second position, pneumatic means including a control valve for actuating said valve moving means to move said valves to their aforesaid second positions, an auxiliary electric circuit including a source of electric energy and an electromagnetic switch for opening and closing the circuit, means operatively associated with said source of power for causing said switch to close said circuit whenever the supply of power is interrupted and to open said circuit when the supply of power is resumed, and electromotive means included in said circuit and operatively connected to said control valve and adapted when energized by the closing of said circuit to actuate the control valve and thereby cause said valve moving means to move said main and tuyere valves to their aforesaid second positions.

11. The combination with a furnace having tuyeres, an air-fuel compartment, a source of compressed air, and a source or electric power for providing the compressed air, or means including a main valve for connecting said compressed air source to said compartment, means including a tuyere valve for selectively connecting the tuyeres either to said compartment or to said compressed air source, said valves being arranged to be moved to either of two operating positions in the first of which the main valve is open to connect said compartment to said compressed air source and the tuyere valve connects the tuyres to said compartment and in the second of which the main valve is closed and the tuyere valve connects the tuyres to said compressed air source, electrically operated means responsive to interruptions oi! power from said power source for causing said valves to move to their aforesaid second positions whenever the supply or power is interrupted but permitting the valves to be returned to their aforesaid first positions when the supply of power is resumed, and latch means for holding said valves in their aforesaid second positions, upontheir being caused to move to such positions by said electrically operated means, until said latch means are released.

ALEXANDER LAIST. EARL MILTON BALDWIN. 

